An arranged marriage is a marriage that was... arranged. It is usually set up by the parents of the two children. Sometimes marriages are arranged to bring peace to the two families, or to give their children a better future by arranging the marriage to be with wealthy (and therefor: stable) people.
A love marriage is a marriage that is made out of... love. The two people met, and found each other attractive enough to get married. What attracted each other could be based on looks, personality, power, or a score of other factors (or a combination of factors).
It's hard to say which type of marriage is better. Love marriages, when based on the wrong things, can be great at first, but grow into horrible abominations. When done right, it is a beautiful bond that will last a lifetime.
Arranged marriages tend to be more stable, but the people in them may not like it.
Basically you have to ask yourself, which is better? A relatively sure thing, or double or nothing? Obviously I'm oversimplifying the issues, but love and marriage are concepts too tough to explain.